A time-resolved fluorescence lateral flow immunochromatographic assay based on oriented immobilized antibodies for the ultrasensitive detection of C-peptides in human serum

C-peptide is a biomarker that has clinical implications for the diagnosis of a variety of diseases. In this study, an ultrasensitive time-resolved fluorescence lateral flow immunochromatographic assay (TRF-LFIA) method was established for the detection of C-peptides in human serum. The key to this method is the oriented immobilization of antibodies anti C-peptide on TRF microspheres that can sufficiently expose the antigen binding site. The limit of detection (LOD) of this method for C-peptide was 0.005 ng mL^-1, which is 10-fold less than that of TRF-LFIA method based on nonoriented immobilizing antibodies. The working range of this method was 0.005-250 ng mL^-1, and the spiked recoveries of C-peptide in human serum were 106.85%-116.40% with a CV value less than 10%. The test results of actual serum samples had good consistency (R² > 0.97) with the Roche Cobas 8000 automatic chemiluminescence immunoassay analyzer. This method can be utilized for the point-of-care testing (POCT) of C-peptide, and the oriented immobilizing method can also be used to construct highly sensitive probes to improve the sensitivity of other analytes in the POCT platform.